In the title compound, [MnCl(2)(C(14)H(12)N(2))]·0.5H(2)O, all of the non-H atoms apart from the Cl atom lie on a mirror plane and the methyl H atoms are disordered over two sites of equal occupancy about the mirror plane. The Mn(II) ion is coordinated in a distorted tetra-hedral environment by two N atoms of the phenanthroline ligand and two chloride ions. A half-occupancy solvent water mol-ecule lies on a mirror plane and close to an inversion center.